I am trying to set an upper limit on the width of a particle. The mass resolution is already determined from MC. The full mass distribution is fitted with the resolution function convoluted with two Gaussians. The plot of the negative profile likelihood ratio is shown below. The result I got from PLC is an interval like
12 +- 15 MeV. How do I turn this into an upper limit? All the examples I saw in the tutorials seen to be based on counting experiments.